1. Field of Invention
The present invention relates to a storage device using a nonvolatile memory such as a flash memory, etc. and a writing method thereof.
2. Description of the Related Art
In recent years, memory cards loaded with a nonvolatile memory as storage media of digital cameras and cellular phones have expanded in their market. As the memory card capacity increases, the applications are expanded from recording with small capacity of data files, still images, and others, to recording with large-capacity required for moving pictures. Consequently, various developments have been made with respect to a recording medium including a nonvolatile memory (for example, patent documents 1 through 4).
In recent years, in a NAND type flash memory primarily used for nonvolatile memory of memory cards, a physical block size which is a data erase unit increases from 16 kB (mainly in a flash memory of 128 MB or smaller) to 128 kB (mainly in a flash memory of 128 MB or larger), as the capacity increases. On the contrary, in a file system which manages data writing to a memory card, a cluster which serves as a data write unit has not been changed and remained 16 kB.
In a conventional small capacity memory card (mainly with capacity of 128 MB or less), the cluster capacity when the data is written to the memory card is equal to the physical block which is the erase unit of the NAND type flash memory included in the memory card.                Patent document 1: JP-A-2001-154909.        Patent document 2: JP-A-11-53248.        Patent document 3: JP-A-2002-324008.        Patent document 4: JP-A-05-216780.        